The present invention relates to a system for inducing a brain wave of the person, and more particularly to a system for providing a relaxation effect and an activation effect in a state of mind of the person.
In the system, the brain wave of the person is induced by a feedback control including a brain of the person. Namely, the brain wave of the person is detected, and a specific element of the brain wave, such as an .alpha. wave is extracted. By using the extracted brain wave, a signal for controlling stimulation by light is produced for inducing a desired brain wave. The stimulating light is applied to the person for stimulating the brain, thereby inducing the desired brain wave. Thus, the desired brain wave can tie powerfully and quickly induced by an induction effect of the feedback control.
Such a system is used for as a sole system, or as a combination system with an audio healing system or a massage device.
FIG. 13 shows a conventional brain wave inducing system employed with a feedback loop structure including a brain of a user. The system comprises a sensor unit 10 for detecting a brain wave of the user, a light signal producing system 20 for extracting a specific element of the brain wave and producing a light stimulation signal, and an actuating unit 30 for applying the stimulating light based on the light stimulation signal to the user.
The sensor unit 10 comprises a headband 11 to be easily put on or removed from a head of the user, and an ear clip 14a detachably clipped on an ear of the user. A pair of electrodes 12 and 13 as brain wave sensors are provided on an inner portion of the headband 11 so that the electrodes are touched on a forehead of the user when the headband 11 is put on the head. The ear clip 14a has an electrode 14 as a brain wave sensor to be touched on the ear.
The actuating unit 30 comprises a capsule or cover 31 to cover the head and face of the user, and a light emitting member 32 provided on an inner portion of the the cover 31 at a position such that the stimulation light is applied to eyes of the user.
The light signal producing system 20 is provided for extracting the specific element of the brain wave and producing a light stimulation signal for controlling stimulation by light based on the extracted brain wave, thereby inducing the desired brain wave. The system comprises a biological amplifier 24 to which outputs of the electrodes 12, 13 and 14 of the sensor unit 10 are connected, an A/D converter 25, an automatic gain control circuit (AGC) 26, a band-pass filter (BPF) 27, a D/A converter 28, and an amplifier 29 connected to the light emitting member 32 of the actuating unit 30.
The electrodes 12 of the sensor unit 10 is connected to a GND input of the amplifier 24, the electrode 13 is connected to a minus input, and the electrode 14 is connected to a plus input, respectively. The amplifier 24 amplifies a very weak brain wave signal detected by the sensor unit 10 to a predetermined value. The amplified brain wave signal is applied to the A/D converter 25 for converting the signal into a digital signal of 8 bits, for example. The digital brain wave signal is applied to the AGC 26 in which the gain of the signal is adjusted for a following stage. The BPF 27 operates to extract a predetermined element of the band of the brain wave signal. The D/A converter 28 converts the extracted band element of the brain wave of the digital signal into an analog signal. The amplifier 30 amplifies the analog signal so as to control the light emitted from the light emitting member 32 of the actuating unit 30.
The light signal producing system 20 further comprises a microprocessor unit (MPU) 22 having a controller 23. The AGC 26 and BPF 27 are operated by programs of the MPU 22. A remote controller 21 is provided for applying external operating commands to the controller 23. The controller 23 controls tasks and other circuits in the system in accordance with the operations of the remote controller 21. For example, the controller 23 produces a message A to initialize the BPF 27, and controls the amplifier 29 of gain variable for adjusting the amount of the stimulation light in accordance with a choice of the user.
In the BPF 27, since the .alpha. wave of the brain wave is effective to provide a relaxation effect, a predetermined band is set based on the .alpha. wave. The .alpha. wave is a basic wave appeared in large amounts when an awakening normal adult rests, and has a feature that the dispersion thereof is small when the person is relaxed in a clearer awakening state. Thus, the BPF 27 has a frequency characteristic of Q=10 (Q=(center frequency f)/(band width the gain of which becomes lower than the gain of the center frequency f by 3 dB)). The .alpha. wave has a waveform having an amplitude between 10 to 100 .mu.V and frequency between 8 to 14 Hz. However, there is an individual difference in .alpha. wave characteristics. Thus, the center frequency of the BPF 27 is set to be varied for covering the range of the frequency.
Furthermore, in the BPF 27, since a proper .alpha. wave is determined in dependency on the person, influence caused by the individual difference is controlled to be absorbed. If a person having a high frequency of .alpha. wave is induced to a range of a low frequency of .alpha. wave, the person may feel bad because of a large difference between the frequencies. In order to solve the problem, at initialization, the BPF 27 operates to change the center frequency step by step to sweep the band of the .alpha. wave. Then, an average frequency of the brain wave signal is calculated to set the center frequency to a value lower than the average value by 0.5 Hz. Thereafter, the center frequency is fixed to the set value during the procedure. Thus, an inconvenience such as a bad feeling is avoided.
Describing the operation of the system, the brain wave of the user is detected by the sensor unit 10. The detected brain wave is amplified by the amplifier 24. The amplified brain wave is applied through the A/D converter 25 and the AGC 26 to the BPF 27 where a proper .alpha. wave is extracted. The extracted brain wave is applied to the amplifier 29 through the D/A converter 28. The amplifier 29 produces an electric signal for light stimulation based on the extracted brain wave. The light stimulating signal is applied to the actuating unit 30. The light emitting member 32 emits the light for stimulation which is applied to the closed eyes of the user, thereby stimulating the brain.
Thus, the user is sufficiently applied with a proper light stimulation produced based on own .alpha. wave to be induced to a relaxed state in a short time.
As hereinbefore described, a main purpose of the conventional brain wave inducing system is to induce the person to a relaxed condition.
However, if the system is provided with not only the relaxation effect but also a sleep inducing effect for positively inducing the person to sleep, the product worth of the system may be increased. In the improvement, economically, it is necessary to lower developing and manufacturing costs as less as possible.
In order to realize the brain wave inducing system provided with the sleep inducing effect in addition to the relaxation effect by using the basic composition of the conventional system with small change, technical means must be designed for the system.
Furthermore, in the conventional system, one of the brain wave sensors is mounted on the head of the user for detecting the brain wave. However, the condition that the sensor is directly mounted on a part of the body may cause the user to be nervous. In such a case, a sufficient sleep inducing effect can not be obtained. If the system is used during sleeping, the system may interfere natural moving such as turning in sleep.
Therefore, it is preferable that the system can be used without mounting sensors on the body.
Furthermore, the ear clip is used as the other brain sensor because the ear is near the brain, and has no muscles. Consequently, noises to be caused by action of the muscle do not produce. In addition, the electrode can be easily attached to the ear by the ear clip.
However, the ear clip stimulates the ear compared with the headband, and may hurt the ear if it is used for a long time.
Therefore, it is desirable that even if the user must mount the sensor on the body, the relaxation and sleep inducing effects, or at least the relaxation effect can be easily obtained.